Imaging Quiz Case 1Mukesh Prasad; John K. Niparko, MD; Baltimore, MdA 50-year-old African American man presented with numbness along the lateral aspect of his right foot that gradually worsened over a 4-month period. A magnetic resonance imaging (MRI) scan was suggestive of a cauda equina tumor, for which the patient underwent an L4-5 hemilaminectomy. No gross abnormality was seen, and histologic examination revealed only fibrous scarring. Postoperatively, the patient experienced numbness involving the left leg and buttocks. One month later he experienced a right-sided facial weakness, diplopia with gaze to the right, decreased sensation to temperature along the lateral aspect of the right foot, and intermittent episodes of vertigo. He denied associated fever, rash, facial numbness, and lymphadenopathy. Two months of treatment with dexamethasone (Decadron) did not change his symptoms. An MRI scan was performed (Figure 1 and Figure 2). Based on the results, the patient underwent a